1. Field of the Invention
The present invention relates to a modified emulsion of polycarbonate resin and a process for production of said emulsion. More particularly, the present invention relates to a polycarbonate emulsion improved in adhesivity, water resistance and chemical resistance, as well as to a process for producing such a polycarbonate resin emulsion.
2. Description of the Prior Art
Polycarbonate resins, which are a thermoplastic resin, are superior in heat resistance, impact resistance, transparency and dimensional stability. Therefore, they are in wide industrial use as molded products such as electric or electronic parts and the like. Moreover, they have come to be used recently also as surface coatings for various base materials, owing to their properties.
These coatings have heretofore been used mainly as a solvent-based coating obtained by dissolving a polycarbonate resin in an organic solvent such as toluene, xylene, acetone, ethyl acetate, butyl acetate, cyclohexanone, methylene chloride, chloroform, dimethyl formamide, tetrahydrofuran, dioxane, dioxolan or the like. In recent years, however, a demand for a water-based coating (using no solvent) has increased in consideration of air pollution, fire hazard and environmental sanitation during application, associated with the solvent-based coating.
With respect to the demand for such a water-based coating containing a polycarbonate resin, there was proposed a process for producing the coating by emulsifying a polycarbonate resin in water using a small amount of an emulsifier. The water-based coating produced by such a process is free from the above-mentioned problems of solvent-based coatings containing a polycarbonate resin.
Water-based coatings containing a polycarbonate resin, however, have the following problems. That is, a polycarbonate resin itself has low adhesivity to a base material; when the polycarbonate resin is made into an aqueous emulsion using an emulsifier, the emulsifier has an adverse effect and, as a result, the polycarbonate resin comes to have even lower adhesivity.
Further, when a water-based coating of polycarbonate resin is applied to form a coating film, an emulsifier remains in the dried coating film and, as a result, the film has reduced water resistance and reduced chemical resistance (these problems can not be ignored).